Residential Well Water: Quick Checklist for Flood Recovery

By: Heather Nix, Water Resource Agent

As we approach the one-year anniversary of Hurricane Helene, many of us are reflecting on – or still recovering from – the damage it caused. One lesson is the importance of being prepared before the next storm arrives.

If your home relies on a private well for drinking water, it’s especially important to know how to disinfect your well after flooding. Floodwater can contaminate private wells with bacteria, sewage, fuel, and other pollutants. If this happens, shock chlorination is the standard way to disinfect it to remove the bacteria. If your well is contaminated with fuel or other pollutants, this method will not be effective. 

Supplies needed:

• Regular, unscented bleach (5-6% sodium hypochlorite) – about 1 gallon
  (Do NOT use: scented, no- or low-splash, or color-safe bleach)
• Waterproof gloves, eye protection
• Small funnel or 5-gallon bucket (optional)
• Tools to open well (if needed)

The Shock Chlorination Process

Below is a simplified overview of the steps. For detailed instructions, see these helpful resources:

• NC Department of Health & Human Services: Disinfecting Your Private Well with Liquid Bleach (https://www.youtube.com/watch?v=cUKxtAbdbEg)
• University of Georgia: Disinfecting Your Well Water: Shock Chlorination (https://fieldreport.caes.uga.edu/publications/C858-4/disinfecting-your-well-water-shock-chlorination-2/)

STEP 1: CONFIRM ELECTRICITY IS OFF

1. Confirm electrical wiring to well has not been damaged and is turned off.
2. If wiring is damaged, do not proceed until it has been repaired and is safe to operate.

STEP 2: INSPECT THE WELL

1. Inspect well for damage (examples: cracked casing, missing cap, broken seal)
2. Inspect well and surrounding area for ongoing contamination (ex: sewer line break, dirty stormwater, oil/gas leaks)
3. The well must be repaired, with no active contamination, for disinfection to provide lasting results.

STEP 3: RUN WATER UNTIL CLEAR

1. Turn power on to well. Use caution!
2. If well is intact and there is no active contamination > run water from outside spigots until it appears clear.
3. Disinfection methods are less effective if water is not clear.

NOTE: If needed, collect water now for use during waiting period.

STEP 4: ADD BLEACH

1. Open well access (ex: plug, air vent, or lift entire well cover)
2. Pour bleach into the well casing. A funnel may help to direct bleach into the well.
3. See Disinfecting Your Water Well (https://dnr.mo.gov/document-search/disinfecting-your-water-well-pub2733/pub2733 ) for instructions on calculating the correct amount of bleach for your well. If you cannot perform the calculations, one (1) gallon bleach is usually (more than) enough per residential well. 

STEP 5: CIRCULATE CHLORINE

1. Run water from outside hose into the well casing until you smell chlorine coming from the hose. Turn off outside hose.
2. Turn on all water faucets, inside and outside, until you smell chlorine at each. Then turn off all faucets.

STEP 6: WAIT

1. Do not use any water during the waiting period. Chlorine requires contact to disinfect.
2. Wait 8-18 hours before turning faucets back on. The high chlorine level will help disinfect the pipes but can be corrosive if left too long (24 hours maximum). *Use caution while any chlorine smell is present – bleach can burn eyes and irritate skin.

STEP 7: FLUSH THE SYSTEM

1. After the waiting period, turn on outside spigot and run water into an area where it will minimize damage (away from septic tanks, streams, etc.). This water contains high levels of chlorine and is not safe for human consumption or contact. The water may be used for cleaning (reminder – bleach may damage fabrics, clothes, etc.).
2. Run water until you no longer smell chlorine odor. Turn the water off.
3. Run water from inside faucets until you no longer smell chlorine odor. Turn the water off.

NOTE: The water should now be disinfected.

STEP 8: TEST THE WATER

1. After 3-7 days, the chlorine smell should be completely gone, and the well water should be tested for bacteria.
2. If available, have water tested professionally.
3. Otherwise, use DIY test kit to indicate presence of bacteria.

Preparing now helps ensure that you’ll be ready to keep your drinking water safe if the next storm impacts your private residential well.